With the advent of substantial new uses for high bandwidth digital and analog electro-optic systems, there exists a greater need to effectively control the routing and switching capability of electro-optic or optical signals from among many possible paths. This is especially true in digital computing systems where signals must be routed among processors; in analog systems such as phased array radar; and in the switching of high bandwidth optical carriers in communication systems. However, it should be realized that these are just several of numerous electro-optic systems which require the use of an optical switching or routing mechanism.
In many current and future systems light beams are modulated in a digital and/or analog fashion and used as “optical carriers” of information. There are many reasons why light beams or optical carriers are preferred in these applications. For example, as the data rate required of such channels increases, the high optical frequencies provide a tremendous improvement in available bandwidth over conventional electrical channels such as formed by wires and coaxial cables. In addition, the energy required to drive and carry high bandwidth signals can be reduced at optical frequencies. Further, optical channels, even those propagating in free space (without waveguides such as optical fibers) can be packed closely and even intersect in space with greatly reduced crosstalk between channels. Finally, operations that are difficult to perform in the lower (e.g., radio) frequencies such as time shifting for phased array applications can often be performed more efficiently and compactly using optical carriers.
A common problem encountered in many applications in which high data rate information is modulated on optical carrier beams is the switching and/or routing of the optical carriers from among an array of channels. These differing optical channels may represent, for example, routes to different processors, receiver locations, or antenna element modules. One approach to accomplish the switching is to extract the information from the optical carrier, use conventional electronic switches, and then re-modulate the optical carrier in the desired channel. However from noise, space, and cost perspectives it may be more desirable to directly switch the route of the optical carrier directly from the input channel to the desired channel.
Specific examples of switching and/or routing systems are systems that separate an array of input channels into even and odd channels or into bands of channels, Interleavers and Band Channelizers, and systems that attenuate (or filter) selected channels. Interleavers, Band Channelizers and Filters perform needed functions in optical communication systems, such as WDM and DWDM systems.
U.S. Pat. No. 5,771,320 discloses a free space optical switching and routing system utilizing a switchable grating based approach together with novel noise suppression techniques. This family of devices provides for an optical switching and routing system that is useful for interconnecting any of an input array's optical channels to any of an output array's optical channels. The invention disclosed in U.S. Pat. No. 5,771,320 has several distinct advantages including compactness, a reduction in insertion loss and the number of required switching devices and control signals.
U.S. Pat. No. 6,072,923 discloses an optical switching and routing system utilizing high efficiency switched mirrors. The switched mirrors can function, for example, by diffraction (diffractive mirrors) or reflection (reflective mirrors) and have the benefits of a lack of dispersion, where the steered direction does not strongly depend on wavelength.
The optical switching and routing system of U.S. Pat. Nos. 5,771,320 and 6,072,923 utilize a series of optical input signals, which form a vertical input array of m optical channels. These optical input signals may either be directly input to the switching and routing system, or they may originate as electrical input signals that are converted into optical signals prior to input in a conventional manner. Accordingly, this input array may include an array of optical fibers, semiconductor lasers (e.g., Vertical Cavity Surface Emitting Lasers or VCSELs), or free space beams.
There is a need for more compact systems, with lower insertion loss.
It is an object of this invention to provide an optical switching and/or routing system that provides for a compact geometry.
It is another object of this invention to provide an optical switching and/or routing system that provides for a low loss one-to-one optical interconnection from a set of input channels to a set of output channels.